When constructing waste deposits, great accuracy is necessary in building watertight base-layers and surface sealings with high-quality mineral materials, consisting mainly of dense clay and soil-bentonite-admixture-liners. The relation between the achieved insitu-soil-density and the water-permeability is being investigated in triaxial permeability-cells and with self-developed insitu-permeability-test-devices. Extensive test-series were carried out to find out the most suitable recipes of bentonite mixed with the original in-situ-material from different sites in order to achieve the lowest coefficient of permeability for each project. The experience of the site-control has a great influence carrying out laboratory tests performed in advance to provide the best quality of the final construction. Also the time-depending development of the permeability is observed in retained undisturbed samples. Also waste mechanics is investigated in the laboratory. It is important for settlement prediction, stability evaluation of slopes and waste-structure interaction. Protecting the environment against leachates out of residual waste deposites, the construction of surrounding cut-off walls is very efficient. Research work for properties of fresh bentonite-slurries and on undisturbed core-samples of the final hardened bentonite admixture is important.